Register control for printing continuous metal strip



Mam}! 1963 R. J. KIECKHEFER, JR 3,081,700

REGISTER CONTROL FOR PRINTING CONTINUOUS METAL STRIP I MUkDOwUd 3,081,700 REGISTER CONTRQL FOR PRINTING CQNTINUQUS METAL TRIP Robert J. Kieckhefer, J12, Barrington, 113., assignor to EJitho-Strip Corporation, Chicago, BL, a corporation of llinois Filed Sept. 20, 1961, Ser. No. 139,466 6 Claims. (Cl. 101-177) This invention relates to apparatus for printing and decorating metal and similar substantially stiff material in continuous strip form, and refers more particularly to means for so controlling the rotation of the impression roller or rollers in such apparatus that the successive impressions made thereby are all located at regularly spaced intervals along the length of the strip.

Printing and lithographing metal and similar substantially stiff materials in continuous strip form presents serious problems not encountered in the web printing of relatively supple materials such as paper, metal foil and fabric. A major problem is synchronizing the rotation of the impression roller, carrying the image to be reproduced, with the lengthwise motion of the strip, so that the successive impressions made by the impression roller are at uniformly spaced predetermined intervals along the strip.

While the term register is usually employed in the graphic arts to denote the correct relationship to one another of two or more successively made impression that occupy a single imprint area on a web or sheet being imprinted, it will be seen that the term is applicable also, at least in an analogous sense, to designate the correct relationship to one another of two or more impressions occupying diiferent but adjacent imprint areas along the length or across the width of a strip or web, and the term register is sometimes used herein in that sense. More specifically, the present invention is concerned with the problem of obtaining register (in the specialized meaning thereof) lengthwise along a strip .or web.

Since a strip which is printed or decorated with lengthwise adjacent impressions that are in register with one another is usually intended to be cut and formed into containers or other articles of manufacture after the printing or decorating operation is performed thereon, the attainment of such register to a high degree of perfection is of the utmost importance in order to insure that the impressions appear in exactly the desired locations on the finished articles when the same are formed from the strip by automatic machinery.

Patent No. 2,890,653, issued June 16, 1959, to F. J. Kinzelman, discusses the problems encountered in obtaining lengthwise register in the printing of metal and similar stiff material in continuous strip form discloses a method and means for achieving such register,

While the apparatus of the Kinzelman patent ha proven to be generally satisfactory in use, it is somewhat complicated and therefore requires well trained personnel to keep it operating properly. Its complexity is in part clue to its inclusion of separate but interconnected means for short term register control and for long term register control. The short term register control insures that register will be maintained as between successively made lengthwise adjacent imp essions, while the long term register control compensates for the cumulative efiect of very slight register errors in the individual impressions, each negligible in itself but together capable of producing an excessive misregister along a substantial length of strip.

For short term register control in the Kinzelman apparatus the strip is trained partway around a backup roller which also serves as a monitor roller. The backup and impression rollers are driven by separate hydraulic motors to which pressure fluid is supplied from a constant pressure variable-volume main pump. The torque thus applied to the rollers is of a constant value such as to rotate them at circumferential speeds that correspond to the nominal local linear speed of the strip at the printing station; but for a number of reasons,'discussed at length in the Kinzelman patent, the actual local linear speed of the strip can and does frequently vary from its nominal speed. To vary the speed of the impression roller so as to maintain it exactly synchronized with the local linear speed of the strip portion with which it is engaged, the backup roller derives energy from the moving strip, through its frictional contact therewith, and applies such energy to the impression roller to modify its speed. To this end the hydraulic motor by which the backup roller is driven is connected in the hydraulic circuit in series between the main pump and the drive motor for the impression roller, and it acts as an auxiliary pump which modifies the output of the main pump to vary the speed of the impression roller drive motor in correspondence with variations in strip speed.

One disadvantage in this short term register system is that slippage between the strip and the backup roller can result in errors in register. Because the backup roller has relatively large mass, and a relatively large amount of energy is therefore requied to change its speed in unison with abupt changes in the local linear speed of the strip, such slippage occurs often enough to be troublesome. Another disadvantage of the Kinzelman arrangement is that the feedback for short term register control is obtained through the long term register control, which also tends to be unreliable at times, due to the need for heavy damping thereof.

The long term register control comprises a socalled walking wheel, which is driven by the impression roller drive motor to rotate at exactly the circumferential speed of the impression roller and which rotates in engagement with the strip at a monitoring station adjacent to the impression roller. The walking wheel is mounted on a lengthwise flexible shaft, and hence when the linear speed of the strip portion engaged therewith varies from the circumferential speed of the walking wheel, the latter moves lengthwise along the strip, in one direction or the other, at a rate dependent upon the discrepancy between the speeds of the strip and the impression roller. By means of a pneumatic mechanism an output is produced which varies with the movement of the Walking wheel lengthwise of the strip and this output is used to vary the displacement of the hydraulic motor which drives the impression roller, to bring the circumferential speed of the impression roller back into synchronism with the speed of the strip.

The efiiciency and dependability of the walking wheel are dependent upon sufiicient flexibility of the shaft by which it is carried to allow the wheel substantial freedom for movement lengthwise of the strip, while at the same time this shaft must be torsionally rigid so that it will satisfactorily transmit rotation to the wheel. These requirements are inconsistent with one another and cannot be fully met in practice. As a compromise a shaft has been used which is too stiff to permit complete freedom of bodily motion of the wheel but which has such torsional flexibility as contributes substantial instability to the system, requiring heavy damping. As a result, the long term register system is incapable of following rapid changes in strip speed; and since rapid strip speed changes are also likely to produce slippage of the strip over the backup roll, the apparatus of the Kinzelman patent affords no dependable means for correcting for errors due to such rapid local accelerations and decelerations of the strip.

Another and very serious disadvantage of the Kinzelman apparatus is that it is speed responsive, rather than being responsive to discrepancies between the actual angular position of the impression roller at any instant and its desired angular position at that instant, its desired angular position being that which it should have if the impression that it is making is to be in register with all other impressions lengthwise along the strip. Thus if a series of impressions is made, each of which is in proper lengthwise register with the others, and then, because of an acceleration of the strip relative to the impression roller, a long impression is made, the series of impressions that follows the long impression may be in register with its trailing edge, and with one another, but they will not necessarily be in register with the impressions of the first series. Eventually the long term register control may bring impressions of the second series back into register with those of the first series, but only after a substantial number of impressions of the second series has been made. The delay in resuming such register will of course be dependent upon the amount of damping incorporated in the long term register system. When the strip thus imprinted is subsequently run through a container forming or cutting machine having automatic indexing means, all of the containers formed on impressions of the second series that are out of register with the impressions of the first series will be defective, so that a substantial portion of the strip following each short or long impression will be wasted.

With the foregoing in mind, it is a general object of the present invention to provide, in apparatus for printing and decorating metal and similar substantially stiff material in continuous strip form, simple and effective means for controlling the rotation of the impression roller to maintain it synchronized with the strip, with its angular position always in proper relation to the portion of the strip with which it is engaged, regardless of transient or localized variations in the speed of that portion of the strip which is passing the impression roller location, so that all of the successive imprints of the impression roller upon the strip will be in lengthwise register with one another along the length of-the strip.

It is another object of this invention to provide for controlling the angular position of a rotating impression roller used for imprinting metal and similar substantially stiff material in continuous strip form, to at all times maintain a fixed relation between such angular position and the relative length of strip material that has been fed past the impression roller, and whereby such control is so accurately maintained as to eliminate the necessity for specialized short term and long term register control instrumentalities.

Another object of this invention is to provide apparatus for register control which achieves the above stated objectives and which allows the strip to follow a straight path through the printing station, if desired, or, if preferred, enables it to be curved partway around the backup roller so as to undergo a change of direction at the printing station, and which, moreover, can be employed with both offset and direct impression printing apparatus.

Still another object of this invention is to provide register control apparatus of the character described having a monitor roller carried by a rigid but freely rotatable shaft and which is rotatably driven by the strip and in turn drives a position responsive electrical instrumentality that presents a light load to the strip through the monitor roller so that the rotational position of the monitor roller is at all times accurately related to the length of the strip that has been fed past it.

While this invention contemplates regulation of the speed of the impression roller as it rotates, for the purpose of continuously controlling the angular position of the impression roller relative to the length of strip fed past it, it is another object of this invention to provide such control of impression roller speed by means of apparatus that is both sensitive and inherently stable, and which is therefore both fast and accurate in its responses.

More specifically, it is a further object of this invention to provide register control apparatus of the character described which comprises a monitor roller, mounted at a monitoring station adjacent to the impression roller and engaged with the strip to be rotated thereby, for producing an output that is a function of the length of the strip fed past the monitoring station, and feedback means directly connected with the impression roller, to be accurately responsive to its angular position, whereby a second output is produced that is balanced against, or compared with, the output produced by the monitor roller to thus yield a control output which is applied to the regulation of the instantaneous angular position of the impression roller, and wherein the magnitude of the control output is always proportional to the amount of discrepancy in the angular position of the impression roller, so that the system is stable and self-damping.

A further specific object of this invention is to provide control apparatus of the character described which comprises comparatively simple and dependable apparatus, much of which is readily available as standard equipment.

With the above and other objects in view which will appear as the description proceeds, this invention resides in the novel apparatus hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawing illustrates one complete example of the physical embodiment of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and in which the single FIGURE is a more or less diagrammatic side perspective view of printing apparatus embodying the principles of this invention.

Referring now to the accompanying drawing, the numeral 5 designates generally a strip of metal or similar stiff material having very substantial length and which is to be imprinted or decorated by means of the apparatus of. this invention, designated generally by 6. In the machine 6 the strip follows a defined path that carries it from a source, such as a supply reel 7, successively through hold back rolls 8, a printing station 9, and pull through rolls 10, and finally to a rewind stand 11 at which the strip is wound into a compact coil. Those skilled in the art will appreciate that there may be additional stations along the path of strip travel, as for example a coating or lacquering station, an oven through which the-strip passes after it leaves the printing station, and a cooler through which it passes after leaving the oven. Only those stations are herein illustrated which are directly related to the imprinting of impressions that are in lengthwise register with one another along the length of the strip.

Regardless of the number and nature of the stations along the path of strip travel, the strip is drawn through the machine by the pull through rolls 10, which are drivingly connected, through transmission means 12, with an electric motor '13 or other drive means. The pull through rolls tend to move the strip lengthwise at a substantially uniform speed, but for a. number of reasons, explained at length in the aforesaid Kinzelman patent, the local linear speed of the strip at any given station in the machine, and notably at the printing station 9 with which this invention is primarily concerned, may fluctuate moreor less substantially above and below the nominal driving speed of the pull through rolls.

To. maintain the strip under some degree of tension as it moves through the machine, and thus constrain it to follow accurately along the path defined by the several rollers that it traverses, the hold back rolls 3 are'provided with suitable rotation inhibiting means (not shown) by which they are caused to resist forward movement of the strip, without, however, actually preventing its advance through the machine. The rewind reel 11 is suitably driven in a manner well known to those skilled in the art so as to wind the strip material into a coil at the same rate that it emerges from the machine.

At the printing station 9 the strip passes through one or more printing couples (two printing couples being shown in the present case), each comprising an impression roller 16 and a backup roller 17. It is not material to the present invention whether the strip follows a perfectly straight path through the printing station or is partially wrapped around each backup roller or otherwise made to undergo one or more changes of direction in the course of its progress through the printing couples, In

the present case the printing couples are shown as being arranged to define a horizontal path along which the strip moves in a straight line through the printing station.

The impression roller 16 of each printing couple can comprise, as shown, a blanket or transfer roller cooperable with a. plate roller 18, as in offset printing, or it could be a roller of the direct impression type. Each of the backup rollers 17 is an idler that rotates in consequence of its circumferential engagement with the strip.

All of the rollers herein mentioned are supported on suitable frame means (not shown) for rotation on axes which are fixed along the path of strip travel and which extend parallel to one another and transversely to the length of the strip.

Each of the impression rollers is driven by a synchronous electric motor 20 or other constant speed prime mover, through variable speed transmission means 22, so that the impression rollers rotate entirely independently of their engagement with the strip. However, by means of the automatic control apparatus hereinafter described, the variable speed transmission means for each impression roller is constantly adusted to maintain the angular position of the impression roller at all times in exactly a predetermined relationship to the length of the strip that has moved past the impression roller, so that each successive impression will occupy a predetermined space along the length of the strip such as to be in lengthwise register with all of the impressions previously made by the impression roller. In most cases the ratio between the rate of angular displacement of the impression roller and the linear speed of the strip is such that the circumferential speed of the impression roller is maintained exactly equal to the local linear speed of the strip, but in some special circumstances the impression roller circumferential speed might be maintained at some other predetermined ratio to strip speed, and even in that case the selected ratio can be exactly and constantly maintained by the method and apparatus of this invention, despite fluctuations in local strip speed.

The variable speed transmission means 22 for each printing couple comprises a pair of transmissions 23 and 48 connected in series. The transmission 23, which is manually controllable, is connected directly to the drive motor 29 and provides for relatively coarse adjustment over a wide range of speeds, to enable the circumferential speed of the impression roller to be brought into approximate equality with linear strip speed, so that the corrections which must be made by the automatic control apparatus will not exceed its operating range. The other transmission 43 is adjusted by means of the control apparatus and is interposed between the manually controlled transmission 23 and the impression roller. The automatically controlled transmission 48 provides for a substantially narrower range of speed variations to enable the control apparatus to effect very fine adjustments of impression roller speed.

In general the control apparatus for each impression roller comprises a monitor roller 24 which is mounted at a location adjacent to the printing couple or couples to have its periphery engaged with the strip for rotation thereby, a self synchronous alternator (sometimes re ferred to as a synchro control transformer, or simply a synchro) 25 which is driven by the monitor roller, a

second synchro 26 which is drivingly connected with the impression roller, an amplifier 27 having output terminals 29 and input terminals 28 into which the output of the synchros is fed, and a two-phase servo motor 30 connected with the output terminals of the amplifier and which effects regulation of the automatically controlled variable speed transmission 48.

The monitor roller 24 rotates on a fixed axis and comprises a wheel having a resilient tire 31 that peripherally engages the strip at a point just ahead of where it enters the printing couples. Preferably the monitor roller is mounted as close as possible to the printing couples to insure that the local linear speed of the strip at the monitoring station is always exactly equal to the local linear speed of that portion of the strip which is engaged by the impression rollers, or, in other words, to insure that the length of strip fed past the monitor roller station always bears an exact relationship to the length that has passed each impression roller. As a result, the angular position of the monitor roller is always exactly a predetermined function of the length of strip that has passed in engagement with each impression roller.

It is desirable that the diameter of the monitor roller be identical to that of the impression rollers, so that the rate of angular displacement of the monitor roller will be the same as that of the impression rollers when the latter are in step with the strip. However, where the circumferential speed of the impression roller is not intended to be equal to the linear speed of the strip, the circumference of the monitor roller will differ from that of the impression roller by such an amount as to give said rollers equal rates of angular displacement when the impression rollers are in step with the strip. Since there must always be a predetermined ratio between the diameters of the monitor and impression rollers, the monitor roller should be detachably secured on its shaft 32 to facilitate setting up the press for different jobs.

The synchros 25 and 26, which are respectively connected by the shafts 32 and 33 to the monitor roller and the impression roller, are conventional position responsive instrumentalities, each capable of producing an output that varies in its characteristics with variations in the angular position of its shaft, or, more accurately, with variations in the angular position of its rotor (not shown). The two synchros should have identical characteristics, and the shafts 32 and 33 which connect them with the respective rollers by which they are driven should be rigid and free from whip and backlash. The shaft 32 for the monitor roller should be supported with particular attention to minimizing rotational friction, so that the monitor roller and its associated synchro present the least possible load to the strip. The synchros of course offer only very light loads to the rollers by which they are driven, and this is particularly important in the case of the monitor roller driven synchro 25 because it assures against slippage between the monitor roller and the strip.

The rotor terminals R1 and R2 of one synchro (in this case the synchro 25 which is driven by the monitor roller) are connected with a source of reference AG. by means of conductors 36 and 37. The corresponding stator terminals S1, S2 and S3 of the two synchros are connected with one another by means of conductors 38, 39 and 40, so that the alternating currents induced in the stator of synchro 25 will have exact counterparts in the stator of synchro 26. Hence the currents in the stator of synchro 26 constitute the output of the synchro 25, since their characteristics at any instant depend upon the angular position at which the rotor of synchro 25 is disposed at that instant by the monitor roller.

The rotor terminals R1 and R2 of synchro 26 are connected With the input terminals 28 of the amplifier 27 by means of conductors 42 and 43. Hence the input to the amplifier represents the combined outputs of the two synchros, and its characteristics are a function of the relative angular positions of their rotors. In a sense, therefore, synchro 26 produces a feedback as well as an output, since the voltage appearing at its terminals R1 and R2 differs in phase from the reference A.C. only when, and to the extent that, the rotor of synchro 26 is disposed at a diiferent angle than the rotor of synchro 25, and this regardless of the absolute speeds of the rotors of the two synchros.

In order to produce a useful error signal, the AC. appearing across the terminals R1 and R2 of synchro 26 must, in effect, be compared with the reference A.C., and this is done by connecting the output terminals 29 of the amplifier, by means of conductors 44, with the terminals 45 of one phase winding of the two-phase servo motor 30, while the reference A.C. source is connected, by means of conductors 46, with the terminals47' of the other phase winding of the servo motor. Thus at any instant the phase relationship between the two alternating currents applied to the servo motor will be a function of the angular relationship of the rotors of the two synchros, or, in other words, of the relationship between the length of strip that has passed the monitor roller, and the position of rotation of the impression roller. The magnitude of any phase difference between said A.C.s will be proportional to the amount of the angular difference between the monitor and impression rollers, and the phase polarity of the error signal will depend upon whether the impression roller is angularly in advance of or behind the monitor roller.

The servo motor will exert no torque when the error signal is zero, because the in-phase A.C.s applied to its respective phase windings will balance or offset one another. When the angular positions of the monitor and impression rollers differ from one another, the amplifier output, being out of phase with the reference A.C., will cause the servo to rotate in the direction to effect an adjustment of the variable speed transmission means by which the speed of the impression roller is increased or decreased to bring it back into angular correspondence with the monitor roller. Since the rate of rotation of the servo motor is proportional to the magnitude of the difference in synchro rotor angles, the servo motor tends to be self damping, and the system therefore has no tendency to hunt.

The manually adjustable variable speed transmission 23 is adapted to be used, in conjunction with a null meter 50, to bring the monitor and impression rollers into approximate, synchronization before the automatic control is placed in operation. The null meter is a D.C. voltmeter of conventional type, so calibrated, however, that its needle is on a zero marker at the center of its scale when a D.C. of one polarity and an arbitrarily selected value is applied to it.

The reference A.C. source is connected to one of the primary windings 52 of a three winding transformer 53 -by means of conductors 54, while the other primary 55 of the transformer is connected with the terminals R1 and R2 of synchro 26 by means of conductors 56 which are in parallel-with the amplifier input leads 42 and 43. The transformer in effect adds the two A.C. voltages algebraically and produces an output in its secondary 57 which is proportional to the difference in their phase. A

phase shift control 58 connected with the terminals of one primary (in this case the primary 55) provides for maintenance of the proper phase relationship between the transformer primary inputs so that when the output of synchro 26 is in phase with the reference A.C. voltage across the transformer secondary will be zero, while if the primary inputs are out of phase the secondary output will be an AC. voltage of a value determined by the transformer ratio.

The A.C.. output of the transformer secondary is rectified and filtered by means of a half-wave rectifier 59 connected in series with the secondary and the meter and a condenser 60 connected across the secondary terminals.

The transformer output is thus applied to the meter as a direct current. A potentiometer 62 in series with the meter and transformer secondary provides for adjustment of the maximum voltage that can be applied to the meter, to maintain the voltage within the scale of he meter while permitting the meter to swing to its maximum reading when the voltages across the two transformer primaries are out of phase.

A source 63 of D.C. bias, in parallel with a zeroing potentiometer 64, is also connected in the meter circuit to bring the meter needle to its center position when the voltages across the transformer primaries are in phase. This is necessary because the meter is a. conventional D.C. voltmeter, and its needle would otherwise swing to one end of the scale (its normal zero position) under these circumstances.

It will be apparent that the direction and extent of displacement of the meter needle from the central zero point will afford an indication of the angular difference be tween the rotors of synchros 25 and 26. However, it should be noted that there is a ambiguity in the system, in that the meter will read zero both when the .two synchro rotors are at exactly corresponding angles and when theyare 180 apart. The latter position, however, is an unstable one for the control system, which it cannot maintain.

With the amplifier off, the adjustments are made with the manual control for the variable speed transmission 23 until the meter needle tends to swing very slowly to opposite sides of its central zero point, indicating that the rotational speeds of the monitor and impression rollers are nearly equal, so that dissimilarities in their relative angular positions are developing quite slowly and within the range of the automatic control.

When, under these conditions, the meter needle swings, to its zero point from one side thereof, the two synchro rotors will have corresponding angles just as it reaches the zero point, and the amplifier can be switchedon at that instant to enable the automatic control system to take over the regulation of the impression roller. When the meter needle swings to its zero point from the other side thereof, the two synchro rotors will be in angular positions that are 180 apart asthe meter needle crosses the zero mark, and if the amplifier were switched on at that time, the system would not have stable operation. However, experience has shown that the manually controllable variable speed transmission 23 enables the circumferential speed of the impression roller to be brought so nearly into synchronism with strip speed that the movement of the meter needle takes place at a very slow rate, and hence it is an easy matter for the operator to turn on the amplifier just as the needle reaches its stable condition null.

It will be understood that the amplifier is either transistorized or, if it has vacuum tubes, the filaments are energized during the preliminary manual adjustment of the apparatus, so that the amplifier goes into operation the moment it is turned on, without an intervening warm-up period.

Where two or more impression rollers are used, they .can be geared together and driven by a single motor and variable speed transmission means, or they can be separately driven, as shown, each by its own motor and varia ble speed transmission means. In the latter case each impression roller is drivingly connected with a synchro 26 that has its stator terminals S1, S2 and S3 connected with the corresponding terminals of the synchro 25 driven by the single monitor roller. Each of the impression roller driven synchros 26 has its rotor terminals R1 and R2 connected to the input terminals of a separate amplifier, which in turn has its output terminals connected to a servo motor 30 for the variable speed transmission means associated with that impression roller.

From the foregoing description taken together with the accompanying drawings, it will be apparent that this invention provides means for so controlling the rotational speed of an impression roller, in apparatus for imprinting metal and other substantially stiff material in continuous strip form, as to at all times maintain its angular position in a predetermined relationship to the length of strip that has passed it, so that all of the successive impressions made by the impression roller are in accurate register with one another along the length of the strip. It will be further apparent that the control apparatus of this invention is simple, dependable and inexpensive, and is capable of keeping the impression roller in step with the strip despite rapid changes in strip speed and without hunting or requiring damping that would slow the responses of the system.

What is claimed as my invention is:

1. In apparatus for printing impressions upon a continuous strip of substantially stiff material such as metal by means of an impression roller which is mounted at a fixed location along a defined path of lengthwise travel of the strip and which is caused to rotate in engagement with the strip as the latter is moved past said location, means for continuously maintaining the angular position of the impression roller in a predetermined relationship rto the length of strip that has been passed in engagement with it, regardless of variations in the speed of strip travel at said location, so that the successive impressions made by the impression roller are at exactly predetermined intervals along the length of the strip, said means comprising: means for moving a strip length- Wise along said defined path; variable speed drive means for rotatably driving the impression roller independently of its engagement with the strip and having a speed control element by which rotational speed of the impression roller can be regulated; a monitor roller mounted for peripheral engagement with the strip, to be rotatably driven thereby, at a monitoring station at which the local linear speed of the strip accurately reflects its local linear speed at said location; a pair of electrical instrumenta'lities, each having a rotatable element and adapted to produce an output electric current which varies in its characteristics with variation in the angular position of its rotatable element; means drivingly connecting the rotatable element of one of said electrical instrumentalities with the monitor roller; means drivingly connecting the rotatable element of the other electrical instrumentality with the variable speed drive means; output producing means, comprising means electrically connecting said two electrical instrumentalities, for producing a control output electric current which has characteristics that vary with changes in the relative angular positions of the rotatable elements of said two electrical instrumentalities; and servo means electrically connected with said output producing means, to be responsive to the output thereof, and drivingly connected with the speed control element of the variable speed drive means to effect corrections in the speed of the impression roller in accordance with changes in the angular relationship between the monitor and impression rollers.

2. In apparatus of the type wherein a continuous strip of substantially stitf material is moved lengthwise along a defined path to have impressions imprinted thereon by means of an impression roller mounted for rotation in engagement with the strip at a fixed location alorFg said defined path, and wherein the impression roller is rotated independently of its engagement with the strip by power drive means, means for maintaining the angular position of the impression roller in a predetermined relationship to the length of strip that has been passed in engagement with it, so that the successive impressions made by the impression roller are at exactly predetermined intervals along the length of the strip, said means comprising: variable speed transmission means connected between the power drive means and the imgaged with the strip at a monitoring station at which the local linear speed of the strip accurately reflects the local linear speed of the strip portion engaged by the impression roller; means drivingly connecting the monitor roller with the rotor of one of said synchros; means drivingly connecting the impression roller with the rotor of the other synchro; an amplifier having input and output terminals; conductor means electrically connecting said synchros with one another and with the input terminals of the amplifier so that the synchros apply an input to the amplifier which is a function of the difference in the relative angular positions of the synchro rotors and hence of the impression roller and the monitor roller; and other conductor means electrically connecting the output terminals of the amplifier with the servo motor in a manner to cause the servo motor to effect changes in the speed of the impression roller by which the latter is brought back into synchronism with the speed of the monitor roller whenever there is a difference in relatively angular positions of said rollers.

3. In apparatus of the type wherein a continuous strip of substantially stiff material is moved lengthwise along a defined path to have impressions imprinted thereon by means of an impression roller mounted for rotation in engagement with the strip at a fixed location along said defined path, and wherein the impression roller is rotated independently of its engagement with the strip by power drive means, means for maintaining the angular position of the impression roller in a predetermined relationship to the length of strip that has been passed in engagement with it, so that the successive impressions made by the impression roller are at exactly predetermined intervals along the length of the strip, said means comprising: variable speed transmission means connected between the power drive means and the impression roller for driving the impression roller at any of a range of speeds, and having a movable control element by which the rotational speed of the impression roller can be regulated; a twophase servo motor drivingly connected with the control element of the variable speed transmission means; a pair of synchros, each having a stator and a rotor; a monitor roller mounted to have its periphery drivingly engaged with the strip at a monitoring station at which the local linear speed of the strip accurately reflects the local linear speed of the strip portion engaged by the impression roller; means drivingly connecting the monitor roller with the rotor of one of said synchros; means drivingly connecting the impression roller with the rotor of the other synchro; means providing a source of reference alternating current; first conductor means connecting said reference A.C. source with one phase winding of the servo motor and with the rotor of one of said synchros; second conductor means connecting the stators of the two synchros; and third conductor means connecting the rotor of the other synchro with the other phase winding of the two phase motor, so that the speed and direction of rotation of the servo motor respectively correspond to the magnitude of any ditference in the relative angular positions of the monitor and impression rollers and to whichever of said rollers is angularly in advance of the other, the connections to the phase windings of the servo motor being so arranged that the servo motor rotates in a direction to bring the impression roller into angular correspondence with the monitor roller.

4. The apparatus of claim 3, further characterized by the fact that said variable speed transmission means comprises a pair of adjustable speed transmissions, each having a driven input member and a driving output member,

one of said adjustabletspeed transmissions being manually controllable and having its driven input member drivingly connected with the power drive means and its driven output member drivingly connected with the driven input member of the other adjustable speed transmission, and said other adjustable speed transmission having said movable control element and having its driving output member d-rivingly connected with the impression roller.

5. In apparatus of the type wherein a continuous strip of substantially stilf material is moved lengthwise along a defined path to have impressions imprinted thereon by means of an impression roller mounted for rotation in engagement With the strip at a fixed location along said defined path, and wherein the impression roller is rotated independently of its engagement with the strip by power drive means, means for maintaining the angular position of the impression roller in a predetermined relationship to the length'of strip that has been passed in engagement with it, so that the successive impressions made by the impression roller are at exactly predetermined intervals along the length of the strip, said means comprising: variable speed transmission means connected between the power drive means and the impression roller :fordriving the impression roller-at any of a range of speeds, said transmission means having a movable control element by which the rotational speed of the impression roller can be regulated; a servo drivingly connected with the control element of the variable speed transmission means; a monitor roller mounted to have its periphery drivingly engaged with the strip at-a monitoring station at which the local linear speed of the strip accurately reflects the local linear speed of the strip portion engaged by the impression roller, sothat the angular position of the monitor roller is at all times an exact function of the length ofstrip that has been rnoved past engagement with the impression roller; a pairof position responsive electrical instrumentalities, each having a rotatable element and adapted to produce an electrical output having characteristicsthat depend upon the angular position of its rotatable element; means drivingly connecting the rotatable element of one of said electrical instrumentalities with the monitor roller; means drivingly connecting the rotatable. element of the other of said electrical instrumentalities with the impression roller; means including conductor means electrically connecting said electrical instrumentalities with one another sothat they produce an electrical control output having characteristics that depend upon the relative angular positions of the monitor and impression rollers; and means including other conductor means electrically connecting said electrical instrumentalities with the servo to render the servo responsive to said control output so that it effects adjustment of the rotational speed of the impression roller to maintain its angular position in correspondence with that of the monitor roller.

6. In apparatus of the type wherein a continuous strip of substantially stitf materialis moved lengthwise along a defined path to have impressions imprinted thereonby means of an impression roller mounted for rotation in engagement with the strip at a fixed location along said defined path, and wherein the impression roller is rotated independently-of its engagement with the strip by power drive means, means for maintaining the angular position of the impression roller in a predetermined relationship to the length of strip that has been passed in engagement with it, so that the successive impressions made by the impression roller are at exactly predetermined intervals along the length of the strip, said means comprising: variable speed transmission means connected between the power drive means and the impression roller for driving the impression roller at any of a range of speeds, said transmission means having a movable control element by which the rotational speed of the impression roller can be regulated; a monitor roller mounted to have its periphery drivingly engaged with the strip at a monitoring station at which the local linear speed of the strip accurately reflects the local linear speed of the strip portion engaged with .the impression roller, so that the angular position of themonitor roller is always an exact function of the length of strip that has been moved past engagement with the impression roller; a pair of position responsive electrical instrumentalities, each having a rotatable elementand adapted to produce an electrical output having characteristics that depend upon the angular position of itsrotatable element; means including conductor means electrically connecting said i electrical instrumentalities with one another so that they cooperate in producing an electrical output having characteristics thatdepend upon the relative angular positions of the monitor and impression rollers; and means electrically connected with said electrical instrumentalities to be responsive to their outputs for producing a visual indication of theangular relationship of themonitor' and impression rollers.

No references cited. 

1. IN APPARATUS FOR PRINTING IMPRESSIONS UPON A CONTINUOUS STRIP OF SUBSTANTIALLY STIFF MATERIAL SUCH AS METAL BY MEANS OF AN IMPRESSION ROLLER WHICH IS MOUNTED AT A FIXED LOCATION ALONG A DEFINED PATH OF LENGTHWISE TRAVEL OF THE STRIP AND WHICH IS CAUSED TO ROTATE IN ENGAGEMENT WITH THE STRIP AS THE LATTER IS MOVED PAST SAID LOCATION, MEANS FOR CONTINUOUSLY MAINTAINING THE ANGULAR POSITION OF THE IMPRESSION ROLLER IN A PREDETERMINED RELATIONSHIP TO THE LENGTH OF STRIP THAT HAS BEEN PASSED IN ENGAGEMENT WITH IT, REGARDLESS OF VARIATIONS IN THE SPEED OF STRIP TRAVEL AT SAID LOCATION, SO THAT THE SUCCESSIVE IMPRESSIONS MADE BY THE IMPRESSION ROLLER ARE AT EXACTLY PREDETERMINED INTERVALS ALONG THE LENGTH OF THE STRIP, SAID MEANS COMPRISING: MEANS FOR MOVING A STRIP LENGTHWISE ALONG SAID DEFINED PATH; VARIABLE SPEED DRIVE MEANS FOR ROTATABLY DRIVING THE IMPRESSION ROLLER INDEPENDENTLY OF ITS ENGAGEMENT WITH THE STRIP AND HAVING A SPEED CONTROL ELEMENT BY WHICH ROTATIONAL SPEED OF THE IMPRESSION ROLLER CAN BE REGULATED; A MONITOR ROLLER MOUNTED FOR PERIPHERAL ENGAGEMENT WITH THE STRIP, TO BE ROTATABLY DRIVEN THEREBY, AT A MONITORING STATION AT WHICH THE LOCAL LINEAR SPEED OF THE STRIP ACCURATELY REFLECTS ITS LOCAL LINEAR SPEED AT SAID LOCATION; A PAIR OF ELECTRICAL INSTRUMENTALITIES, EACH HAVING A ROTATABLE ELEMENT AND ADAPTED TO PRODUCE AN OUTPUT ELECTRIC CURRENT WHICH VARIES IN ITS CHARACTERISTICS WITH VARIATION IN THE ANGULAR POSITION OF ITS ROTATABLE ELEMENT; MEANS DRIVINGLY CONNECTING THE ROTATABLE ELEMENT OF ONE OF SAID ELECTRICAL INSTRUMENTALITIES WITH THE MONITOR ROLLER; MEANS DRIVINGLY CONNECTING THE ROTATABLE ELEMENT OF THE OTHER ELECTRICAL INSTRUMENTALITY WITH THE VARIABLE SPEED DRIVE MEANS; OUTPUT PRODUCING MEANS, COMPRISING MEANS ELECTRICALLY CONNECTING SAID TWO ELECTRICAL INSTRUMENTALITIES, FOR PRODUCING A CONTROL OUTPUT ELECTRIC CURRENT WHICH HAS CHARACTERISTICS THAT VARY WITH CHANGES IN THE RELATIVE ANGULAR POSITIONS OF THE ROTATABLE ELEMENTS OF SAID TWO ELECTRICAL INSTRUMENTALITIES; AND SERVO MEANS ELECTRICALLY CONNECTED WITH SAID OUTPUT PRODUCING MEANS, TO BE RESPONSIVE TO THE OUTPUT THEREOF, AND DRIVINGLY CONNECTED WITH THE SPEED CONTROL ELEMENT OF THE VARIABLE SPEED DRIVE MEANS TO EFFECT CORRECTIONS IN THE SPEED OF THE IMPRESSION ROLLER IN ACCORDANCE WITH CHANGES IN THE ANGULAR RELATIONSHIP BETWEEN THE MONITOR AND IMPRESSION ROLLERS. 